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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 847 · 40 sums
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The method (Inside 180, outside the sum): Angle sum: ∠A + ∠B + ∠C = 180°. Exterior angle = sum of the two interior opposite angles. Right-angled triangle: longest side² = side² + side² (3, 4, 5 and 5, 12, 13 are famous sets). Sides can make a triangle only if the two shorter sides add up to more than the longest side.

NameDateTime takenScore ___ / 40
  1. 1.Can a triangle have sides of 5 cm, 14 cm and 9 cm? (a) Yes (b) No
  2. 2.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  3. 3.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  4. 4.Can a triangle have sides of 21 cm, 8 cm and 10 cm? (a) Yes (b) No
  5. 5.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 102°. What is each of the other two angles (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 81° and angle B = 43°. What is angle C (in degrees)?
  11. 11.In an isosceles triangle, the two equal angles are 76° each. What is the third angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  14. 14.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  15. 15.An exterior angle of a triangle is 124°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  16. 16.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 30° each. What is the third angle (in degrees)?
  18. 18.An exterior angle of a triangle is 65°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  19. 19.In triangle ABC, angle A = 84° and angle B = 57°. What is angle C (in degrees)?
  20. 20.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 74° and 58°. What is the exterior angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  25. 25.In triangle ABC, angle A = 67° and angle B = 40°. What is angle C (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 79° and 21°. What is the exterior angle (in degrees)?
  27. 27.Can a triangle have sides of 7 cm, 9 cm and 10 cm? (a) No (b) Yes
  28. 28.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  29. 29.In triangle ABC, angle A = 29° and angle B = 42°. What is angle C (in degrees)?
  30. 30.An exterior angle of a triangle is 78°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 76° and 63°. What is the exterior angle (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 79° each. What is the third angle (in degrees)?
  34. 34.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  35. 35.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 94°. What is each of the other two angles (in degrees)?
  39. 39.In triangle ABC, angle A = 98° and angle B = 51°. What is angle C (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?

Answer key

  1. No
  2. 25
  3. 8
  4. No
  5. 20
  6. 39
  7. 10
  8. 48
  9. 53
  10. 56
  11. 28
  12. 20
  13. 59
  14. 38
  15. 46
  16. 36
  17. 120
  18. 44
  19. 39
  20. 42
  21. 27
  22. 132
  23. 48
  24. 65
  25. 73
  26. 100
  27. Yes
  28. 10
  29. 109
  30. 28
  31. 62
  32. 139
  33. 22
  34. 51
  35. 48
  36. 15
  37. 100
  38. 43
  39. 31
  40. 71

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